Problem: $-\dfrac{6}{10} + \dfrac{1}{8} = {?}$
Solution: $ = - {\dfrac{6 \times 4}{10 \times 4}} + {\dfrac{1 \times 5}{8 \times 5}} $ $ = - {\dfrac{24}{40}} + {\dfrac{5}{40}} $ $ = - \dfrac{{24} + {5}}{40} $ $ = -\dfrac{19}{40}$